Rural-urban migration or drift (Urbanization) refers to the movement of people from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change.

Unitary system of government may be described as a government organized under a single central government. A Federal system of government is one in which sovereignty is not confined exclusively to either the central government or the component units, but rather, is divided between them.